libvirt: fix native luks encryption failure to find volume_id

Not all volume types put a 'volume_id' entry in the
connection_info['data'] dict. This change uses a new
utility method to look up the volume_id in the connection_info
data dict and if not found there, uses the 'serial' value
from the connection_info, which we know at least gets set
when the DriverVolumeBlockDevice code attaches the volume.

This also has to update pre_live_migration since the connection_info
dict doesn't have a 'volume_id' key in it. It's unclear what
this code was expecting, or if it ever really worked, but since
an attached volume represented by a BlockDeviceMapping here has
a volume_id attribute, we can just use that. As that code path
was never tested, this updates related unit tests and refactors
the tests to actually use the type of DriverVolumeBlockDevice
objects that the ComputeManager would be sending down to the
driver pre_live_migration method. The hard-to-read squashed
dicts in the tests are also re-formatted so a human can actually
read them.

Change-Id: Ie02d298cd92d5b5ebcbbcd2b0e8be01f197bfafb
Closes-Bug: #1746609

1 files changed, 10 insertions, 0 deletions

diff --git a/nova/virt/block_device.py b/nova/virt/block_device.py
index ab5cd09f69..4100928528 100644
--- a/nova/virt/block_device.py
+++ b/nova/virt/block_device.py
@@ -880,3 +880,13 @@ def is_block_device_mapping(bdm):
     return (bdm.source_type in ('image', 'volume', 'snapshot', 'blank')
             and bdm.destination_type == 'volume'
             and is_implemented(bdm))
+
+
+def get_volume_id(connection_info):
+    if connection_info:
+        # Check for volume_id in 'data' and if not there, fallback to
+        # the 'serial' that the DriverVolumeBlockDevice adds during attach.
+        volume_id = connection_info.get('data', {}).get('volume_id')
+        if not volume_id:
+            volume_id = connection_info.get('serial')
+        return volume_id